pacman -S php-fpm php-pgsql php-gd postgresql

initdb --locale=en_US.UTF-8 -E UTF8 -D /var/lib/postgres/data

enable and start postgresql

create a bbs user, and set password:
[postgres@wehack]$ createuser --interactive
[postgres@wehack]$ psql
postgres=# \password bbs

create db:
creatdb -U bbs -d mybb

set pg_hba.conf(/var/lib/postgres/data/pg_hba.conf):
# TYPE  DATABASE        USER            ADDRESS                 METHOD

# "local" is for Unix domain socket connections only
local   all             bbs                                     password
local   all             all                                     peer

import my database backup:
xzcat bbs.sql.xz | psql -U bbs -d mybb

cd /srv/http/sites
tar xvpf bbs.tar.xz

pacman -S opensmtpd
# is the smtpd service really needed?
systemctl enable smtpd
systemctl start smtpd

copy the Caddy conf file...

change DNS record

php extension needed: gd, pgsql